There is an increased awareness and concern for the safety of wheelchair occupants being transported in vehicles While providing impact protection for able-bodied people in public and private vehicles is a difficult engineering problem, it is a far more difficult and complex engineering problem to provide handicapped, wheelchair-bound individuals with the same degree of crashworthiness protection.
The conventional wheelchair is not made with crashworthiness in mind. The light weight bicycle-type wheels are likely to collapse under the high G deceleration forces encountered in collisions at moderate speeds or even in panic braking to avoid such collisions.
Many wheelchair restraint systems are difficult or impossible for a wheelchair occupant to use. Even with help, it may take several minutes to tie down a single wheelchair. This can cause substantial delays when a whole busload of wheelchairs and their occupants are being secured at the beginning of a trip and released at the end of the trip.
Some of the prior art securement systems utilize removable pins engagable with the main wheels. For example, one such device is disclosed in De Long et al. U.S. Pat. No. 4,475,762 entitled "WHEELCHAIR RESTRAINT SYSTEM". As pointed out the weak links in this design are the light weight spoked bicycle wheels which are prone to collapse under high-G forces.
Other securement systems which have been employed since the turn of the century use cables, chains or the like to tie the frame to the floor. Examples are disclosed in Williams U.S. Pat. No. 4,060,271 issued Nov. 29, 1977 on "WHEELCHAIR HOLD DOWN ASSEMBLY" and Stephens U.S. Pat. No. 4,257,644 issued May 24, 1981 on "WHEELCHAIR TIE-DOWN". Many wheelchair occupants find it difficult and time-consuming at best and impossible at worst to tighten a number of chains to the floor. Further, the tension in the chains is reacted by extra loadings on the wheels which can exacerbate their tendency to collapse under crash conditions.
Many conventional systems beef up the frame with special components and extra frame sections with loops or pins engaging counterparts on the floor. The problem with this is that it in effect requires rebuilding of the wheelchair frame. Examples are Constantin U.S. Pat. No. 4,754,946 issued July 5, 1988 on "WHEELCHAIR RESTRAINING DEVICE", Anthony U.S. Pat. No. 4,457,551 issued July 3, 1984 on "VEHICLE SPEED-LOCK WHEELCHAIR RESTRAINT SYSTEM", Peterson U.S. Pat. No. 4,511,171 issued Apr. 16, 1985 on "WHEELCHAIR RESTRAINT", Hart U.S. Pat. No. 4,076,268 issued Feb. 28, 1978 on "SECURING MEANS", and Tenniswood U.S. Pat. No. 4,389,056 issued June 21, 1983 on "WHEELCHAIR".